Rules applied in the cataloguing of jewellery. Jewellery Auction

  • In the cataloguing of jewellery by period and / or

When, in the opinion of the department, a piece of jewellery was made before 1960, an attempt will be made to describe it as belonging to a certain period or style, according to its design, workmanship, characteristics, metal, gems, setting, etc...

Chronologically, the main styles cover approximately the following periods:

Neoclassical 1780-1820
Elizabethan or Victorian 1840-1900
Belle Epoque 1900-1920
Art Nouveau - Modernist 1890-1910
Art Deco 1910-1940
Retro 1940-1955

The term 'antique' is used for pre-1900 jewellery that does not fit into a particular style.

Chronological approximations (early, mid, late, etc...) are used for jewellery from a certain period that does not fit into a particular style or is difficult to date.

If the cataloguing uses the term "style" together with the name of the style, the buyer must consider that the jewellery has been made in a style that is consistent with or copies designs of that period. Thus, for example, a brooch catalogued as "Art Deco style" will be a modern jewel, more or less recent, with the same or similar design to the original from the period 1910-1940; on the other hand, if a jewel is catalogued as "Art Deco" it should be understood as an original piece made in the same period.

  • In the cataloguing of the metal from which the jewellery is made, it should be understood as an original piece of jewellery made in the same period.

The precious metals commonly used in jewellery are gold, platinum and silver. All three in their pure state are too 'white', so - with some exceptions, such as coins - they are used in alloys with other metals (copper, silver, palladium, nickel, zinc, etc.). The percentage of precious metal used in the alloy is expressed in thousandths (1000 thousandths = pure metal) and is indicated in karat (K)

-not to be confused with the metric carat (ct or q) used in the weight- Certain percentages, which vary from country to country, are subject to legal regulations. In Spain, these percentages are called "ley", and are referred to as "oro de ley", "primera ley", "segunda ley", etc...

Contrasts in force in Spain since 1 January 1989:

1st grade   Gold 18K             750/1000            Contrast

2nd grade      14K Gold             583/1000            Contrast Platinum           950/1000           Contrast

1st grade      Silver                 925/1000            Contrast

2nd grade      Silver                 800/1000            Contrast

585 M

Gold can have different colourings, depending on the nature or proportion of the other metals used in the alloy. In some colours (yellow, white, red, pink, greenish) it is possible to achieve the first grade, but in others (black) it is impossible. In the cataloguing, the metal that could be determined by the touch method or similar and its corresponding grade are indicated. However, the lack of international unification of standards, or the absence of such standards in earlier times, means that small differences in alloys cannot be accurately determined with the method used, so this data must be considered as approximate.

The department uses the following designations in the cataloguing: Fine gold or 24K gold

Fine gold, 18K gold or 750 thousandth gold

2nd grade gold, 14K gold or 583 thousandths gold Low gold (for gold of less than 583/1000)

Gold (for gold whose grade could not be determined) Platinum (for both 950 and 900 thousandths)

Silver, sterling silver, sterling silver, 925 silver or sterling silver, 2nd grade silver or 800 thousandth silver.

  • In the cataloguing of the weight of the stones

The department follows the International Standard according to which the weight must be expressed in carats, with two decimal places and the abbreviation ct (carat). According to the same standard, one carat is equivalent to 200 milligrams.

Weights are calculated by mathematical formula - if the setting permits - or by comparison with templates or patterns. The weight of mounted stones should always be considered as approximate, whether it is a single stone, several stones or all the stones set in the same piece of jewellery (total weight).

It should be borne in mind that certain characteristics in the cut modify the theoretical weight provided by the application of a mathematical formula or the shape of a template, so that deviations of 10 or 15% - whether due to under or over weight - should be considered normal. Likewise, in some saddles with closed or covered butts, hidden fillets, double bevels, chiselled settings, etc... or in certain types of carving (antique, irregular, corporeal, etc...), the deviations in the calculation of the weight may be even greater.

  • When cataloguing the colour and purity of diamonds

The determination of these characteristics requires special conditions of observation, lighting and cleaning, and can only be done with certainty when the stones are unmounted. Therefore, if an estimate appears in the catalogue, it should only be considered as an approximate opinion of the department's staff and not as a certification of quality.

Moreover, the differences between one grade and another are so small that the colour of the metal, the setting or the type of setting can distort the true colour and/or camouflage or hide some inclusions that affect the purity.

For all these reasons, the department does not normally indicate them in the catalogue, although it will personally provide its opinion on the matter, if the customer requires it.

However, exceptionally, when these data are considered relevant additional information, approximate gradations will be specified, indicating up to three grades of colour and purity, as a mere quality guideline.

What the department never does is to estimate only colour or only purity, nor to use descriptive adjectives for these grades, both of which are contrary to the International Standards and have no technical value.

  • In cataloguing the types of diamonds

The term 'brilliant' is used exclusively to refer to round cut diamonds with 57 or 58 facets (girdle not included). The rest are described by their corresponding cut or shape names (see table below), using the term 'fancy cut' generically, if necessary.

The single or eight-eight (8/8) cut and the Swiss or sixteenth cut are two small round cuts, with fewer facets than the brilliant cut, widely used in pre-1970 jewellery.

The term 'old cut' or 'old rock' is used to designate non-modern cut diamonds, with defective lapidary characteristics, cut prior to the 20th century. The department describes as 'semi-antique cut' those old cut diamonds, which in its opinion have been re-cut but retain evidence of earlier lapidation.

For coloured stones, the cataloguing usually specifies the shape, as it is much more descriptive. Emerald cuts, in order to avoid confusion (e.g. emerald cut sapphire) or misleading repetitions (emerald cut emerald), are described as qua- drangular; qualified, if necessary, with 'live edge' or 'killed edge'.

The department does not specify, with justified exceptions, opinions on cut quality.

  • In cataloguing the gems

Whenever the setting, size and cut allow objective readings of the optical properties necessary for correct identification, the department specifies the nature of the gemstones set in a jewel (emerald, garnet, topaz, aquamarine, etc...). If this is not possible or in the case of complex identification cabochons, a professional opinion is provided, which in such cases is accompanied by the adverbs possibly or certainly.

The use of artificial stones - imitation or synthetic - has proliferated in recent decades, although their commercial use, in some cases, dates back to the beginning of the 20th century, being frequent even in jewellery of certain styles (Retro, for example).

The department tries to identify the origin, natural or artificial, of the gems it catalogues. It clearly and unambiguously specifies whether they are fine (natural) or fake (artificial). The name of a gemstone without further ado (e.g. sapphire, ruby, etc.) means that it is natural.

The lack of standardised criteria to classify the quality of coloured gemstones means that there is a proliferation of adjectives and gradings of all kinds, most of which are confusing and not very descriptive. In the grading we provide orientative information on certain qualitative aspects of interest, using specific or commercial terms, according to a responsible professional criterion.

  • In the cataloguing of gemstone treatments

Treatments to improve the appearance of gemstones (colour-transparency) are common nowadays. The trade distinguishes between admissible and fraudulent treatments, the latter being rejected and the former sometimes penalised.

The detection of some treatments is complex, especially if the stones are mounted, and sometimes requires controls and analyses that cannot be carried out in the department. However, we personally provide all kinds of information in this respect, as well as our opinion in specific cases. If the client wishes, we can request, at his expense, a gemmological certificate from a prestigious laboratory.

However, in the department we systematically reject gems in which we detect fraudulent treatment, and if we exceptionally accept them, we clearly specify this in the cataloguing.

Regarding the treatments admitted in the trade, we make no mention of them, so it must be understood, as it is common practice, that emeralds are very likely to be oiled and corundums - sapphires and rubies - heated. However, in stones of significant size or price, if we do not see "obvious signs" of heat treatment, we include our opinion.

  • In the cataloguing of "certified" gemstones

When a gemstone is accompanied by a gemmological certificate, we indicate the name of the laboratory that has issued it, the year, the number and the graduations it has carried out; and that this department may or may not share.

As far as certificates of origin of coloured stones are concerned, we only accept reports issued by laboratories that are internationally recognised in this respect. We are at the disposal of our customers to clarify any doubts they may have on this subject.

  • In the cataloguing of pearls

In accordance with International Standards, we use the term "fine pearl" to refer only to natural, uncultivated pearls. If the weight is specified, it is expressed in grains (1/4 carat). The absence of the word "fine" or "natural" implies that in our opinion it is cultured. In old fine pearl necklaces it is common to find some cultured pearls, added later.

The department usually refers to the characteristics that define the quality of the pearls -fine or cultured-: size (weight for fine pearls, diameter for cultured pearls), shape, colour, orientation (lustre) and texture (external appearance). The absence of comments in this respect implies a lack of quality or defects.

By extension, we use the terms "Australian" and "Tahitian" to refer to pearls that have the typical characteristics of so-called "South Sea pearls", or to those with natural dark colouring, although in both cases they may have originated elsewhere.

Freshwater pearls are those, natural or cultured, with or without nuclei, which have not been obtained from the sea.

  • In the cataloguing of watches

The expression "in working order" only indicates that the machinery is working, not that it is accurate. It is therefore quite possible that some watches, especially if they are old, may need to be overhauled and overhauled in order to function properly, which the purchaser must arrange at his own cost and expense.


Although the cataloguing has been carried out to the best of the knowledge and belief of the staff of this department, in accordance with their professional knowledge and experience, our opinion is not a certification of authenticity as most of the jewellery is mounted and generally used.

Buyers should consider certain data (weight) and characteristics (colour, purity) only as approximations.

We also recommend that customers check the condition and measurements of the jewellery they are interested in during the exhibition period prior to the auction in order to avoid problems once they have purchased it.

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